The present invention relates to the therapeutic treatment, by means other than surgical or medicinal means, of a natural canal of the human or animal body, such as a natural passage or a lumen, through which a fluid is passed or flows, in particular a bodily fluid, and whose passage becomes narrowed, or subject to a stenosis or obstruction.
More precisely, the invention relates to the treatment of a natural canal as defined previously, delimited by a living wall, for example a mucous membrane, which is obstructed or whose cross-section becomes narrowed or limited, locally or over the length of the said canal, under the effect of the centripetal compression exerted by a hypertrophic extrinsic tissue. By way of example of such natural canals, mention may be made of the urinary, digestive, gynecological, etc. passages, excluding the upper airways, and by way of examples of such hypertrophic external tissues, mention may be made of malignant and benign tumors of an organ or gland surrounding the said canal.
According to the invention, the term treatment is to be taken to mean intervention on the natural canal, of the physical and/or mechanical type, aimed at restoring the flow in the said canal.
The present invention is now introduced, defined and expanded on with reference to the treatment of obstruction of the prostatic urethra which is due to a benign prostatic hypertrophy (abbreviated to BPH), it being understood that this is one application of the present invention amongst many others. In this particular case, and referring to the general definition given previously, the natural canal is the entirety of the prostatic segment of the urethra, above the sphincter as far as the neck of the urinary bladder, and the periurethral hypertrophic external tissue consists of the benign prostatic adenoma; this adenoma is an adenomyofibroma comprising a glandular, smooth muscle component and connective tissue.
Currently, it is known to treat BPH by thermotherapy, and for this purpose, benign adenoma is selectively destroyed or reduced, by introducing within it or in situ a controlled dose of thermal treatment energy in order to necrose at least part of the adenoma.
"Thermal treatment energy", in the sense of the present description or invention, means both supply of heat, at a therapeutic temperature, for example lying between 45.degree. and 100.degree. C. and supply of cold, at low temperature, for example of the cryogenic type.
And preferably, the dose of thermal treatment energy is introduced selectively within the benign adenoma, via the endocavitary, that is to say endourethral, route by introduction into the urethra of a microwave radiation source, and whilst simultaneously preserving the urethral mucous membrane, by superficial conductive cooling. This technique is now well known under the name of transurethral microwave therapy (abbreviated to TUMT) and can be implemented with various types of equipment available on the market, for example the equipment of the trademark PROSTATRON, sold by the company Technomed International Inc based at Northwoods Business Park, 100 Rosewood Drive, Danvers, Mass. 01930, USA.
This therapy has a tissue effect: the prolonged exposure of the adenomatous tissue at high temperature is responsible for a coagulation necrosis. The obstruction or rupture of the small vessels in the zone treated by the heat is responsible for a prostatic infarction whose starting point is a peripheral thrombosis of the blood capillaries. Macroscopic examination of the coagulated tissue zone shows a thermal lesion which may extend in depth over more than 10 mm from the lumen of the urethra. In contrast, the surface mucosa and submucosa of the urethra are not destroyed because they have been protected during the treatment, over a depth of 2 to 3 mm, by the cooling circuit. Microscopic examination of the microwave thermal lesion shows a destruction of the cells forming the adenoma.
At the clinical level, the improvement in the disorders of the patient has a twofold explanation:
the probable destruction of the neurological receptors responsible for the voiding reflex between the prostatic urethra and the bladder muscle (detrusor); the consequence is, amongst other symptoms, a decrease in the frequency voiding by day and night; this is the therapeutic effect sought by the patient and his doctor
the decrease in the pressure exerted by the adenoma on the urethra: the consequence is an improvement in the urine flow with an improvement of the emptying of the urinary bladder.
This being the case, this therapy has various drawbacks which should be explained.
It causes the rapid appearance of an interstitial edema. It forms in a few hours; it is responsible for an expansion of the adenomatous tissue treated, towards the lumen of the urethra. The edema increases the pressure at the urethra, decreases the urine flow and may be responsible for the occurrence of acute urinary retention. This edema has the consequence, in chronological order:
of a risk of acute urinary retention; the acute urinary retention requires urgent drainage by insertion of a urethral catheter (Foley catheter) or of a suprapubic catheter; the urine is then continuously collected in a collection bag, which represents a significant handicap for the quality of life; the drain is left in place for a few days to several weeks.
a temporary worsening of the urinary disorders, of the order of one to several weeks.
Healing of the lesion generated by the necrosis may occur in the centripetal direction, over several months, in a more or less disordered manner, and possibly in the wrong position, namely with the urethral lumen partially or completely closed, which can completely or partially negate the benefit of TUMT.
The present invention has the general object of overcoming the traditional drawbacks of thermotherapy, whatever the technique used.
The object of the present invention is to increase the efficiency of thermotherapy techniques, whilst decreasing their morbidity.
A further object of the invention is to increase the lumen of the natural canal, until values are obtained of the same order as those obtained by a conventional or endoscopic surgical operation directly on the hypertrophic extrinsic tissue.
Another object of the invention is to shorten the delay of the onset of the therapeutic benefit, since an increase in the lumen of the previously obstructed natural canal can be obtained almost immediately.
A final object of the invention is to decrease the rate of morbidity in thermotherapy in general, for example due to the rapid onset of an edema.